<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        p{
            width: 100px;
            height: 100px;
        }

        div .p2{
            background: red;
        }

        .p3{
            background: green; 
        }
    </style>
</head>
<body>
    <div>
        <p class="p2"></p>
    </div>
    <p class="p3"></p>
</body>
</html>